It has been said that smelt ( seasonally ) make up a majority of salmon ( LL) and trout's diet, suplimented by insects of course.
I have heard conversations, between those who tie flies, that can be heated, about what angle the wing posts should be at for certain dry flys. People will argue till they are blue in the face regarding how closely you match your design to natures.
But, we use shit for smelt patterns.
A Wulf variation :
I am on a quest for a better smelt pattern. I have a week before a big Maine style fishing trip with some of Team Maine, we will be feeding fish who should take a smelt pattern.
I will keep you posted.